Scutinphora puteus is a fast, flying insect that comes in two varieties, visually distinct only in the red or green markings on its exoskeleton. Biologically and behaviorally, the are practically the same. The only real difference between the two is the resource they gather in the expandable sacks on their backs. Scutinphora with green markings gather water, and Scutinphora with red markings gather oil. This unique ability makes Scutinphora a target for both the desert's natural predators and human survivors. Finding a green Scutinphora at the right time could prove to be life-saving, and survivors can use the oil produced by red Scutinphora for a wide variety of purposes.
How does this Giant bug or anything similar evolve and why? and how would humans and other creatures gather their water/oil without killing them?